Flexible endodontic syringe

ABSTRACT

A flexible endodontic syringe for use in performing root canal therapy on a tooth and that is particularly useful for irrigating a root canal possessing a non-linear central axis is presented. The instrument comprises an elongate shank or needle having an enclosed axial channel or lumen. The shank or needle possesses a flexibility sufficient to substantially traverse the entire length of a root canal. A method for irrigating a root canal is also disclosed.

FIELD OF THE INVENTION

[0001] The invention is an apparatus and method for use in dentalapplications. In particular, the invention is an apparatus and methodfor use in endodontic or root canal procedures.

BACKGROUND

[0002] Endodontics or root canal therapy is a well-known dentalprocedure wherein the crown of a diseased tooth is opened to permit thecanal (or canals) of the tooth to be cleaned and filled. In generalterms, a root canal proceeds as follows. The crown of the tooth isopened to expose the root canal. Typical root canals have a non-linearcentral axis, i.e., they are curved, and the curve of the canal can bequite severe. During an endodontic procedure, a series of very delicate,flexible, rotary driven or finger-held instruments or files are used toextirpate or clean out and shape the root canal. These files typicallypossess contoured or rough outer surfaces to enable the endodontist tobreak up and loosen tissue as well as remove infected dentin from thecanal walls within the root canal. Examples of such files are discussedin U.S. Pat. No. 5,713,736 to Heath et al. The endodontist usuallyrotates and reciprocates the file to bring loose tissue and debris outof the root canal.

[0003] The files, however, are incapable of removing all of thenecessary tissue and debris, especially tissue and debris trapped in thesmaller lateral canals extending off the main canal. Thus, Endodontistsremove this tissue and debris by injecting a fluid (typically adisinfecting agent or chelating agent) into the canal to irrigate thecanal. The typical disinfecting fluid is a dilute solution of sodiumhypochlorite. Ethylenediaminetetraacetic acid (EDTA) is a typicalchelating agent.

[0004] Fluid injection is accomplished by means of a hollow needle orsyringe. As used herein, the term needle will generally refer to theelongate, typically metal shank traditionally associated with medicalinjections. The term needle and shank may be used interchangeably hereinunless the context of the description or claims requires otherwise. Theterm syringe is used to encompass both a needle and other elementsnecessary to discharge a fluid from a needle such as a fluid reservoirand plunger. The injection and removal of the solution is referred to as“irrigating” or “aspirating” the canal.

[0005] After irrigation, the cleaned, disinfected and vacant root canalis then obturated or filled, typically with a waxy, rubbery compoundknown as gutta percha. A set of rod-like pluggers similar to the filesused to extirpate the canal force the gutta percha down into the canal.After the canal is filled, the crown of the tooth is repaired therebycompleting the procedure.

[0006] The non-linear structure of root canals presents several problemsfor endodontists. The canal must be cleaned and disinfected but theintegrity of the canal must be maintained. If a stiff file or plugger isused, the distal end of the tool may pierce the sidewall of the canaland destroy the tooth. If a flexible file or plugger is used, it mustmaintain enough rigidity to accomplish the task of removing or insertingmaterial. For many years, a suitable material for making files andpluggers did not exist and endodontists compensated by creating largerentry holes in crowns and using the best materials at hand.

[0007] In the late 1980's and early 1990's, nickel-titanium alloyspossessing superelastic and suitable shape memory properties becameavailable. Instrument companies began manufacturing files and pluggersmade from these alloys. The nickel-titanium files and pluggers allowedthe endodontist to reach the bottom of the root canal without excessiverisk of puncturing the side of the canal.

[0008] Although nickel-titanium files and pluggers improved portions ofthe root canal procedure, problems remain with respect to theirrigation, aspiration and disinfection of the canal. Presently, theirrigation solutions used to clean, disinfect, and remove debris in thecanal are delivered using rigid irrigation needles. These needles aretypically made of stainless steel and possess blunt ends. The distal endof the needle typically possesses slits or other structural componentsto ensure that the solution is distributed both axially and radiallywithin the canal.

[0009] The rigid nature of a stainless steel irrigation syringe preventsan endodontist from reaching the bottom of a root canal with a syringe.Accordingly, an endodontist cannot directly irrigate the distal end ofthe root canal adjacent the apical foramina or a large portion of thecomplex network of fine lateral fissures, tubules and canals that extendfrom the main canal. The bottom of the root canal and the fine web offissures may act as a breeding ground for bacteria that may later leadto a serious infection resulting in failure of the endodontic treatmentand loss of the tooth. Using current syringes, the endodontist must tryto force the solution, through exertion of hydraulic pressure, to thebottom of the canal and into the fine fissures and canals or makegeometric adjustments to the insertion angle. If too much pressure isexerted, the solution may exit the root canal seriously damagingunderlying tissue. Geometric adjustments to the insertion angle toextend the insertion distance may damage the crown. In short, completeirrigation and proper disinfection of the canal cannot be ensured usingknown instruments.

[0010] Accordingly, a need exists for an endodontic instrument thatallows an endodontist to inject irrigation, disinfecting, and debrisremoval solutions adjacent the distal end of a root canal. Such aninstrument must also be compatible with the physical and geometricconstraints imposed by structure of the root canal.

OBJECT AND SUMMARY OF THE INVENTION

[0011] An object of the present invention is to provide an improvedendodontic instrument and method for use in root canal therapy. Afurther object of the invention is to provide an improved endodonticinstrument and method for irrigating and disinfecting root canals duringendodontic procedures. A still further object of the invention is toprovide an improved endodontic instrument and method that allows for theinjection of irrigating and disinfecting solutions at the distal end ofa root canal adjacent the apical foramina.

[0012] The above and other objects and advantages of the presentinvention are achieved in the embodiments illustrated herein by theprovision of an endodontic instrument adapted for use in performing rootcanal therapy on a tooth. The endodontic instrument according to theinvention is particularly useful for irrigating a root canal possessinga non-linear central axis. In one embodiment, the endodontic instrumentaccording to the invention comprises an elongate shank having a firstend and an opposite second end and an enclosed axial channel extendingthe length of the shank for providing fluid communication between thefirst end and the second end. The enclosed axial channel delivers fluidsto areas external to the second end of the shank (i.e., the wall of aroot canal). The instrument also comprises at least one radial orificepositioned adjacent the second end for providing radial dispersion offluid from the orifice. The instrument is further defined as possessinga shank having a flexibility sufficient to substantially traverse theentire length of a root canal having a non-linear central axis andposition the second end of the shank adjacent the distal end of thecurved root canal and the apical foramina.

[0013] In a further embodiment, the invention is a method for irrigatinga root canal possessing a non-linear central axis. The method accordingto the invention comprises transferring a fluid by way of a needle fromthe crown of the tooth along the non-linear central axis of a root canalto a discharge point adjacent the apical foramina. Thereafter, themethod comprises discharging a fluid from an orifice at the distal endof the needle such that a portion of the fluid is discharged along avector that is substantially perpendicular to the openings of the sidecanals and tubules extending from the main root canal and adjacent theapical foramina.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] This invention may be better understood and its numerous objectsand advantages will become apparent to those skilled in the art byreference to the accompanying drawings in which:

[0015]FIG. 1 is a perspective view of an endodontic irrigation needle inaccordance with the invention.

[0016]FIG. 2 is a schematic representation of the irrigation of a rootcanal in accordance with one embodiment of the invention.

[0017]FIG. 3 is a perspective view of one end of a needle.

[0018]FIG. 4 is a cross-sectional view of a needle.

[0019]FIG. 5 is a cross-sectional view of a distal end of a needle.

[0020]FIG. 6 is a cross-sectional view of a needle.

[0021]FIG. 7 is a cross-sectional view of a distal end of a needle.

[0022]FIG. 8 is a cross-sectional view of a needle.

[0023]FIG. 9 is a cross-sectional view of a distal end of a needle.

[0024]FIG. 10 is a side view of a syringe according to the invention.

DETAILED DESCRIPTION

[0025] One embodiment of the claimed invention is an endodonticinstrument adapted for use in performing root canal therapy on a tooth.The claimed invention is particularly useful in irrigating a root canalpossessing a non-linear central axis. Referring now to FIG. 1, theendodontic instrument comprises an elongate shank 10 having a first end12 and an opposite second end 14. As shown in FIG. 3, the second end ofthe shank 14 is preferably rounded or blunt to prevent unwanted breachesof the wall of the root canal. The shape of the second end of the shank,however, may be angled or pointed if desired or needed for a particularapplication.

[0026] An enclosed axial channel or lumen 16, such as those utilized inhypodermic needles, extends the length of the shank. An enclosed axialchannel or lumen 16 is shown schematically by dotted lines in FIG. 4 andin cross-section in FIGS. 5 and 7. The enclosed axial channel 16provides fluid communication (i.e., a pathway for fluid transfer)between the first end 12 of the shank and the second end 14 of the shankand to areas external to the second end of the shank (i.e., the rootcanal).

[0027] At least one radial orifice 18 is positioned adjacent the secondend 14 of the shank. As used herein, the term “radial orifice” isutilized to convey the fact that the instrument according to theinvention delivers fluid in a manner distinctly different fromtraditional needles or syringes used in other medical procedures.Whereas most needles eject fluid along a path aligned with the needle'selongate axis, the instrument according to the invention is designed toeject fluid or cause fluid to eject at an angle oblique from orperpendicular to the shank's elongate axis as shown in FIG. 3. Theradial dispersion of the fluid is accomplished by creating at least oneorifice having at least one cross-sectional plane that is oblique orparallel to the elongate axis of the shank. Such orifices are familiarto those skilled in the art. Further, it is to be understood that theorifices shown in the figures are representative and are not intended tolimit the scope of the invention.

[0028] Referring now to FIGS. 3-7, the shank 10 possesses severalorifices 18 adjacent the second end 14 of the shank. Each orifice 18 isa hole situated along the perimeter of the shank 10. Each orifice 18 orhole possesses at least one cross-sectional plane that is oblique orparallel to the elongate axis of the shank.

[0029] Alternatively, radial dispersion is accomplished by removing aportion of the shanks wall at the terminus of the second end 14 of theshank as shown in FIG. 8. The removal of the wall creates asemi-cylindrical opening 20 at the terminus of the second end 14. Thesemi-cylindrical opening allows at least a portion of the exiting fluidto exit at an angle oblique to the shank's elongate axis.

[0030] The dispersion of the fluid at an angle oblique or perpendicularto the shank's elongate axis is important for a number of reasons. Forexample, a fine web of small canals and tubules extends in alldirections from the main root canal. Known needles are incapable ofejecting irrigating or disinfecting fluid directly at the wall of theroot canal at all points along the curve of the canal. Currently,endodontists must create a hydraulic head in the root canal to force thefluid to the bottom of the canal and into the smaller branch canals. Asdiscussed previously, creating excessive pressures inside the root canalrisks damaging the root canal and should be avoided.

[0031] Referring again to FIG. 4, the shank 10 preferably possessesspaced apart depth calibration markings 22 positioned at intervals alongthe length of the shank. Such depth calibration markings enable theendodontist to determine the depth reached during the procedure. Suchmarkings are well known in the art and may vary in size or spacing.

[0032] Referring now to FIG. 2, the shank 10 substantially traverses theentire length of a root canal having a non-linear central axis to apoint adjacent the distal end of the canal and the apical foramina 11.The shank 10 should be flexible and possess shape memory sufficient toreturn to its original position after bending. Presently, alloys ofnickel and titanium are best suited for the invention's purposes. Inparticular, alloys comprising at least about 30% titanium and at leastabout 50% nickel are preferred. Polymer chemistry may soon providematerials suitable for use as a shank as described by the invention andaccordingly are within the scope of the invention.

[0033] The majority of the shanks utilized in accordance with theinvention will have a uniform diameter from the first end 12 to thesecond end 14. Certain applications, however, may require a taperedshank. Accordingly, the invention encompasses instruments utilizing ashank that is tapered at an included angle of between about ½ and about5 degrees. In other words, the shank tapers from a thicker first end 12to a thinner second end 14.

[0034] The instrument according to the invention further comprises acoupling for establishing fluid communication between the needle and afluid reservoir. Couplings for attaching needles to syringes are wellknown to those skilled in the art.

[0035] Most medical syringes may be used with a variety ofinterchangeable needles of varying diameter and length, as envisioned bythe apparatus according to the invention. In most instances, needles areattached to syringes using a Luer coupling or connector. Luer couplingstypically come in two forms, both of which are attached and detached byapplication of a simple mechanical force. One form is a simple conicaldevice which accepts the needle base. This version is often described asa Luer tip. To detach the needle, one simply pulls it off by applying alinear force.

[0036] The other type is often described as a Luer lock. The Luer lockhas a simple screw thread locking mechanism that permits the base of theneedle to be screwed onto the syringe upon the application of a torqueso that it cannot be pulled without unscrewing. Such connectors are wellknown to those skilled in the art and are the subject of numerouspatents such as U.S. Pat. No. 6,033,386 to Novacek et al.; U.S. Pat. No.5,984,373 to Fitoussi et al.; U.S. Pat. No. 5,047,021 to Utterbery; andU.S. Pat. No. 4,452,473 to Ruschlee.

[0037] Although traditional syringe needle couplings may be utilized inthe practice of the invention, in many instances such couplings are notpractical or even suitable. For example, a patient's mouth opening islimited and it may be impossible for an endodontist to reach a tooth,such as a molar, with a needle attached to a syringe using a traditionallinear coupling.

[0038] Currently, endodontists address this problem by bending the tipsof the stainless steel needles used for irrigation. Typically, a 45°-90°bend is utilized. This functionally transforms the upper portion of theneedle into an extension that allows the lower portion of the needle toreach a tooth and enter it through the crown. The flexible nature of theneedle utilized in the practice of the invention makes this optionimpracticable. Accordingly, the invention may utilize an extended andangled coupling that creates a suitable angle between the fluidreservoir and the needle. An example of such a coupling is shown inFIGS. 2 and 10.

[0039] Referring now to FIG. 10, a connector 40, preferably a Luer typeconnector, is shown. Typically, these connectors are formed of polymers.The connector 40 possesses a first end 42 and a second end 44 and anintermediate portion 46 positioned between the first end 42 and thesecond end 44. The intermediate portion 46 is elongate and forms anangle, identified generally at A in FIG. 10, between the first end 42and the second end 44. The connector also possesses a lumen (not shown)extending its length providing fluid communication between the first end42 and the second end 44.

[0040] The embodiment shown in FIG. 10 is designed such that the needleis fixably attached at the second end 44 while the first end 42 isremovably attached to the distal end of a syringe or fluid reservoir asshown in FIGS. 2 and 10 and discussed below. In this design, thedistance between the angle A and the first end 42 functions as anextension allowing the endodontist to reach and enter teeth easily andcomfortably both for the endodontist and patient.

[0041] A further embodiment of the apparatus according to the inventionencompasses an endodontic irrigation syringe of the type shown in FIG.10. The syringe 30 according to the invention comprises a reservoir forretaining irrigation or disinfecting fluid and means for dispensing afluid from the reservoir. Typically, the function of the reservoir andmeans for dispensing are provided by a hollow, axially elongated barrelor tube 32 and plunger 34 combination commonly associated withhypodermic needles and other such medical devices. The syringe 30further comprises a shank 10 of the type previously discussed that is influid communication with the fluid reservoir, fluid communication isaccomplished by means of the connector 40 that is removably attached tothe distal end of the barrel 32. The connector 40 is of the typepreviously described.

[0042] A still further embodiment of the invention encompasses a methodfor irrigating a root canal possessing a non-linear central axis. Themethod comprises inserting an elongate, hollow and flexible shank orneedle of the type previously discussed into a root canal along a paththat generally follows the non-linear central axis of the root canal. Inthis manner the distal end of the needle and its orifices are positionedadjacent the distal end of the root canal and the apical foramina.

[0043] The insertion of the shank is followed by transferring a fluid,by way of the needle, from the crown of the tooth along the non-linearcentral axis of the root canal to a discharge point adjacent the apicalforamina. Thereafter, the fluid is discharged from an orifice at thedistal end of the needle such that a portion of the fluid is dischargedalong a vector that is substantially perpendicular to the openings ofthe side canals and tubules extending from the main root canal andadjacent the apical foramina. This manner of irrigating and disinfectingprovides a more direct application of fluid to the bottom of the rootcanal and the smaller accessory canals that branch from the main canalthus improving the effectiveness of the overall procedure.

[0044] The invention has been described in detail, with reference tocertain preferred embodiments, in order to enable the reader to practicethe invention without undue experimentation. However, a person havingordinary skill in the art will readily recognize that many of thecomponents and parameters may be varied or modified to a certain extentwithout departing from the scope and spirit of the invention.Furthermore, titles, headings, or the like are provided to enhance thereader's comprehension of this document, and should not be read aslimiting the scope of the present invention. Accordingly, only thefollowing claims and reasonable extensions and equivalents define theintellectual property rights to the invention.

1. An endodontic instrument adapted for use in performing root canaltherapy on a tooth and that is particularly useful for irrigating a rootcanal possessing a nonlinear central axis, the instrument comprising: anelongate shank having a first end and an opposite second end; anenclosed axial channel extending the length of the shank for providingfluid communication between said first end and said second end fordelivering fluids to areas external to said second end of said shank;and at least one radial orifice positioned adjacent said second end forproviding radial dispersion of fluid from said orifice; said shank beingsufficiently flexible to substantially traverse the entire length of aroot canal having a non-linear central axis and position said second endof said shank adjacent the distal end of the curved root canal and theapical foramina.
 2. The endodontic instrument of claim 1 wherein saidsecond end of the shank comprises a blunt end surface.
 3. The endodonticinstrument of claim 1 wherein said orifice comprises at least one holesituated along the perimeter of said shank.
 4. The endodontic instrumentof claim 1 wherein said orifice comprises a semi-cylindrical structureat the terminus of said second end of said shank.
 5. The endodonticinstrument of claim 1 further comprising a plurality of axially spacedapart depth calibration markings positioned along the shank.
 6. Theendodontic instrument of claim 1 wherein the shank of said instrumentcomprises an alloy comprising nickel and titanium.
 7. The endodonticinstrument of claim 6 wherein the shank of said instrument comprises analloy comprising at least about 30% titanium and at least about 50%nickel.
 8. The endodontic instrument of claim 1 wherein the shank ofsaid instrument is tapered at an included angle of between about ½ andabout 5 degrees.
 9. The endodontic instrument of claim 1 furthercomprising a fitting mounted at said first end of the shank, saidfitting for establishing fluid communication between said enclosed axialchannel and a fluid reservoir.
 10. The endodontic instrument of claim 9further comprising a fluid reservoir in fluid communication with saidenclosed axial channel.
 11. An endodontic irrigation syringe comprising:a reservoir for retaining a fluid; a needle in fluid communication withsaid reservoir, said needle comprising an elongate shank having a firstend and an opposite second end and an enclosed axial channel extendingthe length of the shank for providing fluid communication between saidreservoir and said second end and for delivering fluids to areasexternal to said second end of said shank, said shank being sufficientlyflexible to substantially traverse the entire length of a root canalhaving a non-linear central axis and position said second end of saidshank adjacent the distal end of the curved root canal and the apicalforamina; at least one radial orifice positioned adjacent said secondend for providing radial dispersion of fluid from said orifice; andmeans for dispensing a fluid from said reservoir to said channel of saidneedle.
 12. The endodontic irrigation syringe of claim 11 wherein saidsecond end of the shank comprises a blunt end surface.
 13. Theendodontic irrigation syringe of claim 11 wherein said orifice comprisesat least one hole situated along the perimeter of said shank.
 14. Theendodontic irrigation syringe of claim 11 wherein said orifice comprisesa semi-cylindrical structure at the terminus of said second end of saidshank positioned along the shank.
 15. The endodontic irrigation syringeof claim 11 wherein the shank of said needle comprises an alloycomprising nickel and titanium.
 16. The endodontic irrigation syringe ofclaim 15 wherein the shank of said needle comprises an alloy comprisingat least about 30% titanium and at least about 50% nickel.
 17. Theendodontic irrigation syringe of claim 11 wherein the shank of saidneedle is tapered at an included angle of between about ½ and about 5degrees.
 18. A method for irrigating a root canal possessing anon-linear central axis, the method comprising: transferring a fluid byway of a needle from the crown of the tooth along the non-linear centralaxis of the root canal to a discharge point adjacent the apical foraminaand thereafter discharging the fluid from an orifice at the distal endof the needle such that a portion of the fluid is dischargedsubstantially perpendicularly to the openings of the side canals andtubules extending from the main root canal and adjacent the apicalforamina.
 19. A method according to claim 18 in which the fluidcomprises at least one fluid selected from the group consisting ofdisinfecting agents and chelating agents.
 20. A method according toclaim 19 wherein the disinfecting agent is sodium hypochlorite and thechelating agent is EDTA.
 21. A method according to claim 18 wherein saidorifice comprises a semi-cylindrical structure at the terminus of thedistal end of the needle.
 22. A method according to claim 18 furthercomprising adjusting the depth of insertion by measuring a plurality ofaxially spaced apart depth calibration markings positioned along theneedle.
 23. A method according to claim 18 wherein the needle comprisesan alloy comprising nickel and titanium.
 24. A method according to claim23 wherein the needle comprises an alloy comprising at least about 30%titanium and at least about 50% nickel.
 25. A method according to claim18 wherein the needle is tapered at an included angle of between about ½and about 5 degrees.
 26. A method for irrigating the distal end of aroot canal possessing a nonlinear central axis, the method comprising:inserting an elongate, hollow and flexible shank having a first end andan opposite second end into a root canal along a path that generallyfollows the nonlinear central axis of the root canal and positioning thesecond end of the shank adjacent the distal end of the root canal andthe apical foramina; and injecting an irrigation fluid into the distalend of the root canal through an orifice adjacent the second end of theshank whereby at least a portion of the irrigation fluid impacts thesidewall of the root canal at an angle that is substantiallyperpendicular to the central axis of the root canal.
 27. A methodaccording to claim 26 in which the irrigating fluid is selected from thegroup comprising disinfecting agents and chelating agents.
 28. A methodaccording to claim 26 wherein said second end of the shank comprises ablunt end surface.
 29. A method according to claim 26 wherein saidorifice comprises at least one hole situated along the perimeter of theshank.
 30. A method according to claim 26 wherein said orifice comprisesa semi-cylindrical structure at the terminus of the second end of theshank.
 31. A method according to claim 26 further comprising adjustingthe depth of insertion by measuring a plurality of axially spaced apartdepth calibration markings positioned along the shank.
 32. A methodaccording to claim 26 wherein the shank comprises an alloy comprisingnickel and titanium.
 33. A method according to claim 32 wherein theshank comprises an alloy comprising at least about 30% titanium and atleast about 50% nickel.
 34. A method according to claim 26 wherein theshank is tapered at an included angle of between about ½ and about 5degrees.
 35. A Luer type connector having a first end and a second end,said first and second ends being separated by an intermediate portion,said intermediate portion being substantially cylindrical and nonlinearand forming an angle between said first end and said second end andhaving a lumen extending its length providing fluid communicationbetween said first end and said second end.
 36. A connector according toclaim 35 wherein the distance between the origin of said angle and saidfirst end is greater than the distance between the origin of said angleand said second end.
 37. A connector according to claim 35 wherein saidconnector is made of a polymer.
 38. A syringe comprising: a hollow,axially elongated barrel; a needle; a removable connector attached tosaid barrel adjacent a distal end thereof said connector comprising afirst end removably attached to said distal end of said barrel and asecond end attached to said needle, said first and second ends beingseparated by an intermediate portion, said intermediate portion beingnon-linear and forming an angle between said first end and said secondend, said connector further comprising a lumen extending the lengththereof and providing fluid communication between said barrel and saidneedle; said needle comprising an elongate shank having a first end andan opposite second end and an enclosed axial channel extending thelength of the shank for providing fluid communication between saidbarrel and said second end of said shank and for delivering fluids toareas external to said second end of said shank, said shank beingsufficiently flexible to substantially traverse the entire length of aroot canal having a non-linear central axis and position said second endof said shank adjacent the distal end of the curved root canal and theapical foramina; at least one radial orifice positioned adjacent saidsecond end of said shank for providing radial dispersion of fluid fromsaid orifice; and means for dispensing a fluid from said barrel to saidchannel of said needle.
 39. The syringe of claim 38 wherein said secondend of said shank comprises a blunt end surface.
 40. The syringe ofclaim 38 wherein said connector is removable from said barrel inresponse to the application of a torque.
 41. The syringe of claim 38wherein said connector is removable from said barrel in response to theapplication of a linear force.
 42. The syringe of claim 38 wherein saidshank of said needle comprises an alloy comprising nickel and titanium.43. The syringe of claim 43 wherein the shank of said needle comprisesan alloy comprising at least about 30% titanium and at least about 50%nickel.
 44. The syringe of claim 38 wherein said angle is selected fromthe group consisting of obtuse and right angles.